The present invention relates to pulse generators for generating pulses having predetermined slopes, comprising a capacitor that can be charged and discharged through predetermined current sources, a switching device for connecting and disconnecting the current sources and a step function signal source for controlling the switching device.
In a pulse generator of this type, the rise and drop times of the generated pulses can be independently regulated by corresponding regulation of the current source.
However, the circuit is restricted to relatively long rise and drop times since the capacitance of the capacitor must be high as compared to the stray capacitance of the switching device. Short rise and drop times in the range of nanoseconds require an extremely small capacitor which does no longer differ substantially from the stray capacitance of the switching device. In this case, however, the stray capacitance and the capacitor form together a voltage divider which superimposes a specific fraction of the step function signal of the capacitor voltage and, thus, the output pulse signal. This in turn results in disturbing steps in the slope of the pulse.